Deltatheridium fossil map
Where fossils of Deltatheridium have been found, shown on the Earth as it looked about 75 million years ago and on today’s map.
Dots are fossil collections recorded in the Paleobiology Database. The “then” view moves today’s fossil sites back to their positions 75 million years ago (the time slice nearest the median age of the fossils) using the Merdith et al. (2021) plate model; positions are approximate. Open on the timeline map →
| Group | Early mammals |
|---|---|
| Lived | 83.6–72.2 million years ago (Campanian) |
| Periods | Cretaceous |
| Family | Deltatheridiidae |
| Named by | Gregory and Simpson 1926 |
| Fossil records | 14 occurrences at 7 locations (PBDB) |
| Found in | Mongolia, Kazakhstan |
| Rock formations | Baruungoyot, Djadokhta, Dabrazhin |
About Deltatheridium
Deltatheridium (meaning triangle beast or delta beast) is an extinct species of metatherian. It lived in what is now Mongolia during the Upper Cretaceous, circa 80 million years ago. A study in 2022 strongly suggested that Deltatheridium was a marsupial, making it the earliest known member of this group.
It had a length of about 15 cm (5.9 in). Its teeth indicate it was carnivorous. One specimen of Archaeornithoides might attest to an attack by this mammal, the skull bearing tooth marks that match its teeth.
Text in “About” is quoted from the Wikipedia article Deltatheridium (revision 1381432944), licensed under CC BY-SA 4.0; introduction excerpted verbatim, formatting removed. Ages, family, authority and fossil records: Paleobiology Database, accessed 23 October 2026. Ages are those of the rock layers the fossils were found in. Wikidata: Q903626.
